The cellular phone industry is constantly challenged in the market place for high audio quality, low-cost products. Motorola's iDEN technology has traditionally reached a fleet service workforce creating a demand for high audio speakerphones. The high audio speakerphones allow a user to engage in a voice conversation without having to hold the phone to the ear. Further, with the demand to make products smaller and with more features, speakerphone designs have started to include the high-audio speaker (transducer) within the mechanical housing of the phone to decrease product size. The transducer is positioned behind the keys to project audio through the keypad.
Many phones have silicone keypads with discrete keys that project upwards between the openings of a plastic housing grill. The rubber keys can be a continuous part of a silicone membrane which serves as the keypad. The housing grill can be a part of the mechanical casing of the phone. The housing grill can include a cross-section of plastic strips over the keypad area that have a minimal width specified by the strength of the plastic, or material. The rubber keys which have height are aligned apart from one another creating a trough that allows for the placement of the housing grill. The plastic strips rest within the channels of the keypad thereby separating the keys.
Ports are generally drilled or cut through the keypad to allow air to flow through the housing grill openings for passing sound. The ports are placed at locations on the keypad which are covered, or hidden, by the housing grill. For example, holes are created behind the plastic strips of the housing grill such that an opening is created to allow air to flow from the speaker through the rubber keypad and up through the ports under the plastic strips and then between the openings of the housing grill. The ports are positioned below the plastic strips of the housing grill such that a user cannot see the openings, i.e. the user only sees the housing grill which covers the openings, and not the hole openings below the plastic cross strips.
Recently, zero-gap keypads have been introduced for use with cell phones to make keypads smaller in line with demand for smaller products. The zero-gap keypads have minimal space between the keys. The keys are abutted next to one another with minimal gap between them. However, a slight gap exists to avoid the physical friction between keys as a user depresses a key. Unlike the regular silicone keypads which have space between the keys, the zero-gap keypads have no room to allow the plastic cross-section strips of a housing grill. In practice, this makes zero-gap keypads attractive because they require less material, are more compact, and provide similar function to normal keypads. Accordingly, zero-gap keypads generally lack a housing grill over the keypad to cover the space between the keys. The zero-gap keys are also interconnected by a silicone membrane which can be seen on fine inspection of the keypad.
The zero-gap keypad has a continuous membrane like the regular rubber keypads. High audio ports cut at positions on the membrane between the keys, to allow high audio to pass, will be seen by the user, particularly during lighted dialing. The zero-gap keys, even though considered zero-gap, have finite space between the keys, and the silicone membrane can be seen through the zero gap spaces. For example, port openings positioned between the zero-gap keys can be seen when the light reflects off the port openings during lighted keypad mode. Additionally, the keys on a zero-gap keypad are generally vertical without overhang, and do not allow ports to be drilled under the keys.